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SpringMVC RedirectView的使用以及源码分析

看一段普通的代码,我们访问controller中的一个方法后,重定向到另外一个controller或者视图。

    @RequestMapping(params="method=index")    public ModelAndView index() {        RedirectView redirectView = new RedirectView("/Demo.do?method=index2", true, true);        ModelAndView mav = new ModelAndView(redirectView);        mav.addObject("attr1", "attr1Value");        mav.addObject("attr2", "attr2Value");        return mav;    }

浏览器的URL会变成http://localhost:8080/FuDeKang/Demo.do?method=index2&attr2=attr2Value&attr1=attr1Value

也就是说Spring会自定把model中的键值放入到URL当中,那么Spring是如何做到的呢,我么还来看ModelAndViewMethodReturnValueHandler这个类。

 

public class ModelAndViewMethodReturnValueHandler implements HandlerMethodReturnValueHandler {    public boolean supportsReturnType(MethodParameter returnType) {        return ModelAndView.class.isAssignableFrom(returnType.getParameterType());    }    public void handleReturnValue(            Object returnValue, MethodParameter returnType,            ModelAndViewContainer mavContainer, NativeWebRequest webRequest)            throws Exception {        if (returnValue =http://www.mamicode.com/= null) {            mavContainer.setRequestHandled(true);            return;        }        ModelAndView mav = (ModelAndView) returnValue;        if (mav.isReference()) {            String viewName = mav.getViewName();            mavContainer.setViewName(viewName);            if (viewName != null && viewName.startsWith("redirect:")) {                mavContainer.setRedirectModelScenario(true);            }        }        else {            View view = mav.getView();            mavContainer.setView(view);            if (view instanceof SmartView) {                if (((SmartView) view).isRedirectView()) {                    mavContainer.setRedirectModelScenario(true);                }            }        }        mavContainer.addAllAttributes(mav.getModel());    }}

 

其中最后一句是关键,首先modelandview当中的model数据全部放到ModelAndViewContainer 里面。

因为我们是重定向,所以无论如何底层最后产生的视图对象都是RedirectView实例,我们在看一下它的源码。

    /**     * Convert model to request parameters and redirect to the given URL.     * @see #appendQueryProperties     * @see #sendRedirect     */    @Override    protected void renderMergedOutputModel(            Map<String, Object> model, HttpServletRequest request, HttpServletResponse response)            throws IOException {        String targetUrl = createTargetUrl(model, request);        targetUrl = updateTargetUrl(targetUrl, model, request, response);                FlashMap flashMap = RequestContextUtils.getOutputFlashMap(request);        if (!CollectionUtils.isEmpty(flashMap)) {            UriComponents uriComponents = UriComponentsBuilder.fromUriString(targetUrl).build();            flashMap.setTargetRequestPath(uriComponents.getPath());            flashMap.addTargetRequestParams(uriComponents.getQueryParams());        }        FlashMapManager flashMapManager = RequestContextUtils.getFlashMapManager(request);        flashMapManager.saveOutputFlashMap(flashMap, request, response);        sendRedirect(request, response, targetUrl.toString(), this.http10Compatible);    }

 

其中  targetUrl = updateTargetUrl(targetUrl, model, request, response);  是拼接了URL的代码,最后调用sendRedirect做重定向。

 

SpringMVC RedirectView的使用以及源码分析